Waterbeds have enjoyed an enormous growth in popularity in recent years, due in large part to their well deserved reputation for unsurpassed sleeping comfort. The buoyant effect of the watermattress provides equal support to all parts of the body, allowing complete relaxation.
One characteristic of the unadorned watermattress which some individuals find pleasurable and others find disturbing is the tendency of wave motion to propagate through the water in the mattress and be reflected from the sides of the bed. Typically this wave motion has a resonant frequency which is dependent upon the size of the mattress and the pressure of the water within the mattress. Many individuals who are accustomed to the solid support of more traditional bed constructions find that the motion imparted to the body by waves propagating through the mattress is distruptive to sound sleep and other bedroom pursuits.
To minimize or alleviate the wave motion problems associated with watermattresses, many modifications have been developed for watermattresses. Among these are Gel substances which may be added to the water to increase the viscosity and decrease the wave propagation, or air chambers disposed within the watermattress to absorb some of the wave energy. Another solution known to the prior art is to provide baffles within the watermattress to join the upper and lower sheets of the watermattress and minimize the displacement created by wave motion in the mattress.
The typical baffled watermattress construction known in the prior art includes an upper and lower sheet which are joined at their confronting edges to define a sealed, water retaining bladder. A plurality of baffles are usually secured within the bladder, and are joined to the upper and lower sheets with simple buttwelds. The baffle members are usually disposed in parallel relationship, although some constructions have used conical baffle members extending axially between the upper and lower sheets.
A serious drawback to the prior art baffle constructions has been the weakness of the buttweld joining the baffle member to the upper or lower sheet. It is well known by those skilled in the art of assembling watermattress of polyvinyl material that buttwelds exhibit far more shear strength than tensile strength. Unfortunately, wave motion propagating through a watermattress causes relative displacement between the upper and lower sheets of the mattress, and this in turn creates tensile stress on the butt seam joining the baffle to the upper or lower sheet. Likewise, over inflation of the mattress will also increase the tensile stress of the buttwelds.
It has been found that the buttwelds in baffled watermattress constructions tend to weaken and fail long before the failure of the edge seams which seal together the top and bottom sheets. When the butt seams fail, the baffle may tear away from the top and bottom sheet, thus reducing the wave damping action of the baffle construction. In other cases, the entire butt seam area may tear away from the top or bottom sheet, causing a catastrophic leak in the watermattress.